The present invention relates to a technique of cleaning automatically a blanket cylinder of a printing press by pressing a cleaning cloth to the blanket cylinder. More particularly, the present invention relates to an automatic blanket cleaning technique of a printing press which also has an automatic rewinding mechanism on the side of a supply roll of a cleaning cloth and rewinds part of the used cleaning cloth after one cleaning cycle is completed in order to use it once again during part of the next cleaning cycle.
A cleaning technique is heretofore known which has the fundamental structure wherein a cleaning cloth supplied from a supply roll is taken up by a take-up roller through a press member and is pressed to a blanket cylinder by the press member to clean the blanket cylinder.
Various structures have been developed and proposed for the press member. For example, Japanese Patent Laid-Open No. 51-56306/1976 teaches the use of a press roller while Japanese Patent Laid-Open No. 55-148164/1980 discloses the press member of the type wherein a rubber tube is inflated by air.
A non-woven fabric or the like has been used as the cleaning cloth. Generally, the non-woven fabric is supplied from a manufacturer under the state where a predetermined length of the non-woven fabric is wound on a paper bobbin. After the roll of non-woven fabric is set as a supply roll to a cleaning apparatus, the tip of the non-woven fabric is fitted to a take-up roller for use.
Cleaning is made by transferring the non-woven fabric either intermittently or continuously from the supply roll to the take-up roller and pressing the cleaning cloth to the surface of the blanket cylinder to be cleaned by the press member during this transfer process. At this time the cleaning cycle is employed wherein the cleaning cloth is dampened appropriately by a cleaning liquid such as a solvent or water to dissolve ink components or the like that adhere to the blanket cylinder and they are then wiped away by the portions of the cleaning cloth that are not dampened by the cleaning liquid. Accordingly, in accordance with the prior art technique, the cleaning cloth has been supplied always unidirectionally from the supply roll to the take-up roller.
As described above, the non-woven fabric as the cleaning cloth is generally supplied under the state where the non-woven fabric of about 10 to 12 m is wound onto one paper bobbin. About 40 cm of non-woven fabric is used in one cleaning cycle in a newspaper offset press while about 15 to about 20 cm of non-woven fabric is used in a sheet offset press and the cleaning liquid is sprayed once or several times to dampen the non-woven fabric for cleaning. The portions of the non-woven fabric dampened by the cleaning liquid are used for dissolving the ink adhering to the blanket cylinder while its dry portions are used for wiping.
Cleaning is made twice or thrice a day in the case of newspaper printing, for example. Therefore, one roll of non-woven fabric is used up within eight to ten days and must be replaced by a new one.
Since the blanket cleaning apparatus of the printing press is the one that is directed to save labor, it is desired to reduce the frequency of replacement of expendables as much as possible and to reduce the cost of operation.